linux-kernel - Re: [PATCH] RDMA/nldev: Fix multiple potential NULL pointer dereferences

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Date:   Fri, 09 Feb 2018 07:36:49 -0600
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/nldev: Fix multiple potential NULL pointer
 dereferences

Hi Leon,

Quoting Leon Romanovsky <leon@...nel.org>:

> On Fri, Feb 09, 2018 at 12:37:02AM -0600, Gustavo A. R. Silva wrote:
>> In case the message header and payload cannot be stored, function
>> nlmsg_put returns null.
>>
>> Fix this by adding multiple sanity checks and avoid a potential
>> null dereference on _nlh_ when calling nlmsg_end.
>>
>> Addresses-Coverity-ID: 1454215 ("Dereference null return value")
>> Addresses-Coverity-ID: 1454223 ("Dereference null return value")
>> Addresses-Coverity-ID: 1454224 ("Dereference null return value")
>> Addresses-Coverity-ID: 1464669 ("Dereference null return value")
>> Addresses-Coverity-ID: 1464670 ("Dereference null return value")
>> Addresses-Coverity-ID: 1464672 ("Dereference null return value")
>> Fixes: e5c9469efcb1 ("RDMA/netlink: Add nldev device doit implementation")
>> Fixes: c3f66f7b0052 ("RDMA/netlink: Implement nldev port doit callback")
>> Fixes: 7d02f605f0dc ("RDMA/netlink: Add nldev port dumpit implementation")
>> Fixes: b5fa635aab8f ("RDMA/nldev: Provide detailed QP information")
>> Fixes: bf3c5a93c523 ("RDMA/nldev: Provide global resource utilization")
>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>> ---
>>  drivers/infiniband/core/nldev.c | 26 +++++++++++++++++++++++++-
>>  1 file changed, 25 insertions(+), 1 deletion(-)
>>
>
> It will be much better to fix the tool instead of fixing ghost case.
> This scenario is impossible for all those flows.
> We can receive the skv/msg in two ways:
>  * First by allocating new message with NLMSG_DEFAULT_SIZE, which  
> has more room
>    than nlmsg_total_size(payload), payload is 0.
>  * Second by getting from netlink.c and it will be at least "struct  
> nlmsghdr" too.
>
> Can you please add this info to the commit message?
>

Actually, I was planing to send a new version of this patch. This time  
using the unlikely macro for all the null checks on nlh.

What do you think?

Thanks
--
Gustavo